Nimonic Fasteners
Manufacturer
India · Mumbai
What Is Nimonic — Alloy Chemistry and High-Temperature Mechanism
Nimonic is a proprietary family of nickel-chromium (Ni-Cr) precipitation-hardened superalloys originally developed by Wiggin Alloys (now Special Metals / PCC) in the UK during the 1940s for Whittle jet engine turbine blades. The Nimonic designation (Nimonic 75, 80A, 90, 105, 115, C263) identifies grades within this family by their composition and mechanical property profile. They are the oldest and most established precipitation-hardened nickel superalloys still in active use.
The high-temperature strength mechanism in Nimonic alloys is gamma-prime (γ’) precipitation hardening — a coherent Ni₃(Al,Ti) precipitate that forms in the nickel matrix during age hardening heat treatment. These fine, coherent precipitates resist dislocation movement at high temperatures, providing creep resistance and maintained strength at temperatures where standard austenitic stainless steels (321, 310S) and even Incoloy 800H deform. Nimonic 80A and 90 maintain useful tensile strength to 850–950°C; Nimonic C263 maintains strength to approximately 900°C with good oxidation resistance.
The key differentiation from Inconel 718 and 625: Nimonic grades are primarily UK/European aerospace and gas turbine specifications — procured to British Standards (BS HR series) and used where European/UK aerospace supply chains are the design authority. Inconel 718 is primarily US/ASTM. For Indian EPC projects with European gas turbine OEM supply chains (Siemens, GE, Rolls-Royce), Nimonic grade specifications appear regularly in fastener MRs alongside or instead of Inconel designations.
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | Balance | — |
| Chromium (Cr) | 18.0 | 21.0 |
| Titanium (Ti) | 1.8 | 2.7 |
| Aluminium (Al) | 1.0 | 1.8 |
| Carbon (C) | — | 0.10 |
| Iron (Fe) | — | 3.0 |
| Cobalt (Co) | — | 2.0 |
| Manganese (Mn) | — | 1.0 |
Nimonic Grade Profiles — 75 · 80A · 90 · C263
Each Nimonic grade is precipitation-hardened with increasing alloy complexity — from Nimonic 75 (simple Ni-Cr, solid solution) through 80A (γ’ hardened Ti+Al) and 90 (higher Co + Ti + Al) to C263 (Co-Mo strengthened, maximum creep resistance). All four grades available as fasteners from ASTM/BS-certified bar stock.
Nimonic 75
Nimonic 80A
Nimonic 90
Nimonic C263
Nimonic Fastener Types & Standards
Nimonic 80A and C263 are primary stocking grades. Nimonic 75 and 90 available on order. All forms from BS HR / AMS / ASTM-certified bar stock, chemical analysis verified before machining. M4–M36.
Nimonic Stud Bolts
Fully threaded and equal-end stud bolts in Nimonic 80A (N07080, BS HR1), 90 (N07090, BS HR2), and C263 (N07263, BS HR40) in solution-annealed and aged condition. Gas turbine casing flanges, industrial turbine hot-section flanges, aerospace engine structural connections, and exhaust system flanges. M6–M36, lengths to 500mm. Chemical analysis certificate with every lot.
Hex Bolts
Full thread and partial thread hex bolts in Nimonic 80A, 90, and C263. M4–M36. Gas turbine structural hex bolts, aerospace nacelle hex bolts, industrial furnace high-temperature structural bolts operating 700–950°C, and combustion equipment structural connections where 310S or Incoloy 800H is insufficient and Nimonic-grade precipitation hardening is specified.
Hex Nuts
Standard hex and heavy hex nuts in Nimonic 80A, 90, and C263. M4–M36. Matched from same BS HR-certified bar as stud bolts for single chemical analysis certificate covering the complete assembly. For gas turbine and aerospace fastener assemblies where all components must be the same Nimonic grade to eliminate dissimilar-metal galvanic contact and ensure matched thermal expansion at service temperature.
Washers
Plain flat washers in Nimonic 80A and C263. M4–M36. Matched from same certified bar as stud bolts and nuts. For gas turbine and aerospace hot-section assemblies requiring complete Nimonic bolt assembly traceability — one chemical analysis certificate covering stud bolt, nut, and washer from the same bar stock batch.
Socket Cap Screws
Hex socket cylindrical head cap screws in Nimonic 80A, C263. M4–M24. Gas turbine combustion liner fasteners, aerospace nacelle access panel screws, hot-section internal fixtures, and confined-access high-temperature bolting in jet engine and industrial gas turbine systems where Nimonic’s creep resistance and oxidation resistance are the design basis.
Custom Nimonic
Non-standard configurations, special head forms, inch UNC/UNF thread, and drawing-specific designs in any Nimonic grade. Aerospace and gas turbine OEM-specific fasteners machined to drawing in Nimonic 80A or C263, with chemical analysis certificate and dimensional inspection report per piece. Contact sales@akbarfasteners.in with grade, drawing, and material certification requirement.
Nimonic 80A vs Inconel 718 vs SS 310S — Grade Matrix
Nimonic occupies a specific niche: UK/European aerospace and gas turbine fastener specifications above SS 310S temperature ceiling and in parallel with Inconel 718. This matrix identifies when Nimonic is the correct or required specification.
| Criterion | Nimonic 80A / C263 This Page | SS 310S | Incoloy 800H | Inconel 718 |
|---|---|---|---|---|
| TEMPERATURE & STRENGTH | ||||
| Max service temperature | 950°C+ (80A/90) | 1040°C (oxidation only) | 982°C | ~650°C strength |
| Creep resistance at 800°C | ✔ Excellent (γ’ hardened) | Poor — creeps | Good | Limited at 800°C |
| Min UTS (hardened) | ≥1250 MPa (80A aged) | ≥515 MPa | ~450 MPa (HT) | ≥1241 MPa (718) |
| Hardening mechanism | γ’ Ni₃(TiAl) precipitation | Annealed only | Carbide precipitation | γ” Ni₃Nb + γ’ |
| SPECIFICATION SYSTEM | ||||
| Primary procurement standard | BS HR1/HR2/HR40 | ASTM A276 S31008 | ASTM B408 | AMS 5663 / ASTM B637 |
| European/UK aerospace | ✔ Standard specification | Below temp range | Structural only | Also used (US AMS) |
| Gas turbine (Siemens/RR/GE) | ✔ Rolls-Royce / Siemens std | Not for hot section | Not for hot section | GE / Pratt primary |
| COST POSITION | ||||
| Relative cost vs 316L | 8–14× 316L | 2.5–3.5× | 5–7× | 10–16× |
For US aerospace/ASTM specs: Inconel 718 (AMS 5663) · For >1040°C: Inconel 601
Nimonic Application Areas
Gas turbine and jet engine hot-section bolting, aerospace structural fasteners, industrial furnace hardware, and defence propulsion systems — wherever precipitation-hardened nickel superalloy is specified at temperatures above SS 310S capability.
Gas Turbine Engines
hot-section exhaust flanges
Jet Engine / Aerospace
nacelle structural fasteners
Power Generation
Siemens / GE turbine sets
Defence Propulsion
defence gas turbine sets
Industrial Furnaces
950°C+ atmosphere structural
Petrochemical HT
reformer >950°C connections
Nuclear
gas-cooled reactor (AGR)
Space / Rocket Propulsion
rocket engine structural
Nimonic Standards Coverage
Same ISO 9001:2015 quality system as our complete exotic alloy range. Chemical analysis by XRF and ICP-OES before machining on every Nimonic order.
Complete Documentation Package
BS HR / AMS Stated
ICP-OES 12-Element
Conformance
Tensile · Hardness
TÜV · BV · Lloyds
Related Superalloy Fastener Grades
Nimonic for UK/European gas turbine and aerospace specs. Inconel 718 for US/ASTM aerospace. Incoloy 800H for process industry high-temperature. SS 310S for sub-1040°C oxidation.
Inconel 718 Fasteners
The US/ASTM equivalent specification for gas turbine and aerospace bolting where AMS 5663 (Inconel 718) is the design authority rather than BS HR1/HR40. For Pratt & Whitney, Boeing, and GE Aviation supply chains specifying Inconel 718 rather than Nimonic grades.
View Inconel Range →Inconel 600 / 601
For oxidising service above 1040°C where Nimonic’s temperature ceiling is exceeded — Inconel 601’s 23% Cr and Al addition provides oxidation resistance to 1250°C for combustion hardware above the Nimonic service range.
View Inconel Range →Incoloy 800H / 800HT
For process industry high-temperature structural applications (steam reformers, ethylene crackers) where Nimonic’s aerospace/gas turbine pricing is not justified — Incoloy 800H provides high-temperature strength and oxidation resistance in a lower-cost Ni-Fe-Cr alloy to 982°C.
View Incoloy Range →SS 310S Fasteners
Below the Nimonic temperature/strength range — SS 310S (25%Cr, 20%Ni, 1040°C oxidation) is the correct and significantly lower-cost choice for applications where creep strength is not the design criterion and oxidation resistance alone is required up to 1040°C.
View SS 310S Page →Need Nimonic
Fasteners?
Grade (75/80A/90/C263) · product form · size · BS HR / AMS / UNS certification · documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in